1. Field of the Invention
The present invention relates to an electrically conductive composition used to fill via-holes provided in ceramic or glass substrates or the like, and more particularly to an electrically conductive composition that is able to prevent entrapment of air when printing an electrically conductive composition into via-holes. In addition, the present invention relates to electronic components using this electrically conductive composition and to a method for producing those electronic devices.
2. Technical Background
Sites referred to as via-holes filled with an electrically conductive metal are formed in single-layer circuit substrates or laminated circuit substrates, in which a plurality of circuit substrates have been laminated, to improve continuity in the vertical direction (both directions or the direction of lamination) or thermal conductivity. An example of a typical process used to form these via-holes comprises: (1) preparing an electrically conductive paste, (2) filling the electrically conductive paste into sites where holes corresponding to via-holes are formed, and (3) drying and firing the paste.
An example of the art relating to an electrically conductive paste for via-holes is JP2003-324268. A paste containing 31.3 to 47.6 vol % of an electrically conductive metal (Ag) is used in the examples of JP2003-324268.
The paste is typically filled by screen printing. As shown in FIG. 1 (conventional art), an electrically conductive paste 10 is filled into holes on a substrate 20 through a metal mask 30. Since the paste has a certain degree of viscosity, when the paste is supplied, it may flow into the hole along the side walls of the hole and entrap air. If the paste is pushed into the hole using a squeegee 40 while in this state, the paste is filled into the hole with air still entrapped therein, thus, forming an air void 50. This entrapment of air is particularly prominent in cases of holes having a large diameter.
Thus, air is entrapped in via-holes with electrically conductive paste during via-hole printing. This causes structural defects such as voids and pin-holes after firing the substrate. These defects have a detrimental influence on electrical and thermal conductivity as well as on the smoothness of the fired surface.